A display device using an organic electroluminescent (EL) element is known as an example of a display device using a current-driven light-emitting element.
An organic EL display device using a self-luminous organic EL element does not require a backlight, which a liquid-crystal display device requires, and therefore is most suitable when a thinner display device is desired. Since there is no limit on a viewing angle of the organic EL display device, the organic EL device is expected to be put to practical use as a next-generation display device. The organic EL element used in the organic EL display device is different from a liquid-crystal cell in that luminance of each light-emitting element is controlled by a value of a current flowing therethrough whereas the liquid-crystal cell is controlled by a voltage applied thereto.
As just described, the organic EL display device, which is a device having almost the same structure as the liquid-crystal display device, can be provided as a ultra-thin, light-weight display for the above-mentioned reason that no backlights are necessary. In this case, structures other than an organic EL display panel need to be made thinner. The size of a power supply device, among the structures other than the organic EL display panel, depends on power consumption of the organic EL display panel, and therefore it is difficult to simply make the power supply device thinner.
For example, FIG. 1 of Patent Literature (PTL) 1 discloses, as a power supply in an organic light emitting diode (OLED) display, two power source circuits connected in parallel for an input voltage. Specifically, a +ELVDD power source circuit and a −ELVSS power source circuit are included as the two power source circuits. The +ELVDD power source circuit generates a +ELVDD voltage of a ELVDD power source which is supplied to a pixel (PX) of the OLED display. The −ELVSS power source circuit generates a −ELVSS voltage of a ELVSS power source which is supplied to a pixel (PX) of the OLED display.